Parametric Design Study on Aerodynamic Characteristics of Variable Pitot Inlets for Transonic and Supersonic Civil Aviation

Abstract

This paper reveals the influence of selected geometric parameters on the aerodynamic performance of circular variable aero engine inlets in transonic and supersonic civil aviation. The trade-off in inlet design and aerodynamic evaluation parameters are presented. The approach to investigate the dependencies between the aerodynamic and geometric parameters at different flight conditions by means of a parametric design study is introduced. The dependencies of inlet drag and efficiency from geometric parameters at flight speeds of Mach 0.95 up to Mach 1.6 are identified. Although entailing additional weight, the inlet length represents the parameter with the highest potential for drag reduction by up to 50% in the selected design space. Ideal geometries for variable pitot inlets are determined. After considering weight, their potential range benefit nearly disappears for subsonic applications, but remains above 20% for supersonic flight at Mach 1.6.

A Variable Pitot-Inlet Concept for Supersonic Aviation

“…During the geometric design, it has been determined that the concept should only adjust two different geometries to minimise its complexity; one geometry for subsonic and one for supersonic flight, both highly efficient and reliable at the respective conditions (Kazula et al, 2019b). This way, an aircraft with variable inlets instead of rigid ones would achieve a range benefit of about 35% at a supersonic flight speed of Mach 1.6 without considering additional weight and aerodynamic losses due to steps and gaps (Kazula et al, 2019a), (Kazula et al, 2019c).…”

“…Although components, such as the ice protections system, the steel net, locking system, wires and screws, must be considered, an additional concept weight of less than 500 kg compared to rigid subsonic inlets is certainly achievable. Without considering the aerodynamic influence of steps and gaps, this results in a range benefit of at least 20%, when applying this concept up to Mach 1.6 (Kazula et al, 2019c).…”

“…Variable pitot inlets for SST applications up to Mach 1.6 offer higher aerodynamic benefits, which could compensate these limitations (Kazula et al, 2019b). Furthermore, variable pitot inlets have several advantages over other supersonic inlet types in terms of flow uniformity, length and weight.…”

Evaluation of Variable Pitot Inlet Concepts for Transonic and Supersonic Civil Aviation

“…Flow separations and potentially resulting hazardous events during take-off and climb operation up to Mach 0.3 need to be avoided by a thick and round inlet lip, which results in increased drag, especially during cruise operation [13]. High efficiency at fast subsonic cruise flight above Mach 0.8 can be obtained by using a thinner lip contour combined with a curved and long forebody, resulting in minimised drag [14], [6]. For supersonic flight up to Mach 1.6, pitot inlets with sharp inlet lips and long flat forebodies can be applied without significant aerodynamic losses [14].…”

“…Hence, within the scope of a feasibility study for variable inlet concepts, the methodological development process is combined with the safety assessment process in aviation according to Aerospace Recommended Practices ARP 4754A [5]. Among others, this process comprises  the identification of ideal geometries for variable inlets concerning drag and flow uniformity for flight speeds up to Mach 1.6 and their potential range benefit [6],  the development of inlet concept groups that adjust the geometry by rigid segment repositioning, by elastic surface deformation or by boundary layer control [7],  the application of the safety methods Functional Hazard Assessment (FHA), Fault Tree Analysis (FTA) and Common Cause Analysis (CCA) [8], [9],  the integration of ice detection and protection systems for variable inlet concepts [10]  as well as subsequent design adaptations. This paper describes the selection of the ideal group of variable inlet concepts by utilising results of aerodynamic investigations, system safety analyses and integration studies.…”